Celtic steel – an evaluation of depot finds

In the course of archaeological excavations on the Gründberg in Linz/Austria, several depots containing a total of 45 steel objects were discovered. These depots had been set up around 100 before Christ (BC). 25 objects were used to take samples for metallographic and microanalytical investigations. In the exercise of his trade, the Celtic smith could resort to different steel grades: non‐alloyed, carbon alloyed, phosphorus alloyed. The technique applied was that of fire‐forging single pieces of steel ‐ which had previously been widened by hammering – to give flat bars showing a multi‐layer structure. For workpieces with special requirements with regard both to hardness and to toughness, a number of carefully selected flat bars with differing contents of alloying metals were bonded by forge welding, which produced a compound material. Hardening by cold working as well as by torquing was already known to these Celtic craftsmen. To obtain tools with a hard edge and a tough core, cementation was used.     

1Cr12型耐热钢棒锻造工艺对横向冲击功的影响

为了开发纵横向性能一致的叶片钢,对锻造工艺进行了改进。选取4种不同锻造工艺的成品,在边部、半径1/2处、中心部位进行取样,测量其性能,结果表明:1Cr12型耐热钢棒在δ-Fe铁素体质量分数小于0.2%,w(S)为0.001%,钢具有高的洁净度的情况下,采用快锻机四镦四拔锻造,锻制钢棒纵、横向冲击功的比值达到1.16~1.26;若采用快锻机墩拔开坯与精锻机联合成材,锻制棒材纵横向冲击功比值可达到不大于1.06。     

Duplex Stainless Steels ‐ a Review after DSS ‘07 held in Grado

Duplex stainless have always been an exiting area of interest for researchers, stainless steel producers, fabricators and end users. They present very diversified technical challenges and simultaneously attractive in‐service properties at excellent cost/properties ratios, particularly in critical markets including oil and gas, chemical industry, pulp and paper industry, water systems, desalination plants, pollution control equipments, chemical tankers, etc. This explains why although they still remain a marginal production in the stainless steel business (less than 1%) dedicated international conferences have been organised since about 25 years. The purpose of this paper is to present a review of the 100 scientific contributions presented during the latest international duplex stainless steel conference witch took place in Grado, Italy, on 18‐20 June 2007. The main topics concerned microstructure and mechanical properties, weldability, corrosion resistance and in‐service properties. The “standard” duplex stainless steels, i.e. the 2304, 2205, and the family of 2507 (Cu,W, ...) grades were confirmed as very valuable grades with outstanding performances proven in more than 20 years successful in‐service applications. New grades including the so‐called lean duplex dedicated to volume oriented markets (possible replacement of 304/316 grades) and some “niche” grades dedicated to very specific markets were presented. It was pointed out that the duplex grades start to be well established products particularly suitable for corrosion resistance applications. They show a two‐digit yearly growth thanks to the production of new grades and production ranges (coils and bars) targeting the replacement of the more costly 300 series including 304 but also rusty carbon steel in e.g. structural application.     

Thermodynamic Activities of “FeO” in some Binary “FeO”‐Containing Slags

In the present investigation, experimental measurements of the thermodynamic activities of iron oxide in the Al₂O₃‐“FeO”, CaO‐“FeO” and “FeO”‐SiO₂ systems were performed in the temperature range 1823‐1873 K by using gas equilibration technique. The molten slag, kept in a Pt‐crucible was brought to equilibrium with a gas mixture of known oxygen partial pressure. A part of the Fe from the “FeO” was reduced during the equilibration and got dissolved in the Pt phase. The samples were quenched after the required equilibration time and the slag phase as well as the platinum crucible was subjected to chemical analysis. The activities of “FeO” in the slag were calculated from the experimental data using thermodynamic information on the Fe‐Pt binary metallic system generated and assessed earlier. The experimental results are compared with earlier thermodynamic studies of the slag systems. Reassessment with the KTH slag model is performed and the results are compared with other thermodynamic models, viz. F*A*C*T? and Thermo‐Calc? respectively. The experimental activities predicted by the KTH slag model are in good agreement with the experimental data available in the literature. A general agreement between the various models is also observed.     

Carbide Evolution in Temper Embrittled NiCrMoV Bainitic Steel

Phosphorus segregation to prior austenite grain boundaries in low alloy steel from exposure to temperatures of 300 to 600°C results in a susceptibility for intergranular fracture referred to as “temper embrittlement”. It has been observed that alloying steel with Mo greatly reduces the phosphorus segregation kinetics. Therefore changes in the ferrite matrix composition from carbide precipitation and evolution involving Mo can influence the segregation phenomenon and fracture properties. This study uses analytical electron microscopy of extraction replicas to characterize the changes in carbide chemistry of a NiCrMoV bainitic steel with 0.25 wt% C that accompany the phosphorus segregation during aging at 480°C for up to 3400 hr. The steel was doped with 0.02 wt% P and tempered at 650°C to two different hardness levels, i.e., two different initial carbide distributions. The amount of grain boundary phosphorus segregation produced by aging at 480°C correlates with the level of molybdenum that remains in solution in the ferritic matrix whereas changes in vanadium and chromium appear to have less influence on the temper embrittlement.     

HRB400Ⅲ钢筋抗震性能研究

从强度与塑性的配合、应变时效敏感性、低温脆性、可焊性等方面对Ф20mm牌号为20MnSiV HRB400Ⅲ钢筋的抗震性能进行了系统的测试和研究。结果表明,钢筋应变时效后韧脆转变温度较高,低温抗震性能差;钢筋碳当量高,焊接性能有待改善;微观分析和成分分析结果表明,为加强钢筋的抗震性能,微合金元素应当适当调整。     

Nb微合金化对齿轮钢高温渗碳奥氏体晶粒度的影响

摘要：通过Nb微合金化提高渗碳温度是当前发展高端齿轮钢的重要思路。以20Cr钢为基准成分,通过实验室熔炼、锻造以及977~1134℃范围内高温伪渗碳实验,研究了0.02%、0.04%、0.06%、0.08%等不同Nb质量分数下渗碳后的奥氏体晶粒结构。在此基础上,依据热力学计算及析出颗粒熟化模型,对AlN、Nb(C,N)颗粒的钉扎强度进行估算并与晶粒尺寸建立联系,得到了适用于含Al、Nb齿轮钢的奥氏体晶粒度控制预测模型。最后,依据此模型分析了Nb含量对20Cr钢渗碳温度的影响,并基于高温渗碳目标提出了Nb微合金化的成分建议。     

Transformation Conditions ‐ Microstructures ‐ Mechanical Properties Relationship in 0.60%C Hypoeutectoid Steel

The relationship between transformation conditions, microstructures and mechanical properties were investigated on a 0.60%C hypoeutectoid steel, which has predominantly pearlitic microstructure. The steel had been austenized at 850‐1050 °C and then isothermally transformed at 570‐660 °C. Afterwards, the microstructures were analyzed by optical microscope, scanning electron microscope, and quantitative metallography. And the mechanical properties were determined. The results indicated that the interlamellar spacing, the pearlitic colony size and the proeutectoid ferrite content follow a linear relationship with the reciprocal of the undercooling, and the strength, the hardness and the toughness follow a Hall‐Petch type of relationship with the inverse of the square root of the interlamellar spacing. Besides, the stress condition should be taken into account during analyzing the effect of the interlamellar spacing on the mechanical properties. The results have been explained on the basis of transformation conditions ‐ microsturctures ‐ mechanical properties ralationship.     

粉末锻造齿轮材料的组织与性能研究

粉末锻造(粉锻)技术结合了粉末冶金技术和精密锻造技术的优点,对烧结的预压件进行一次锻打即可生产出精度高、力学性能强的近净成形产品。本文选择一款齿轮材料(Q61),通过压制、脱脂、烧结工艺获得标准块预压件,然后进行闭模热锻获得致密的标准块。对标准块进行物理性能(密度、硬度、拉伸性能、疲劳性能等)测试和微观组织表征。结果表明,获得的Q61粉锻标准块基本完全致密,密度为7.87 g·cm^-3;空冷硬度约为HRC 25.3,淬火硬度约为HRC 62.1,空冷态较低的硬度为零件后续机加工、整形提供了保证,后续淬火获得的高硬度可节省渗碳工序;标准块抗拉强度达到1052.8 MPa,可与常用齿轮钢性能媲美。本文采用粉锻技术,成功制备出高质量行星直齿轮,其齿部高频淬火后硬度与渗碳齿轮的硬度相当。该工作为粉末锻造技术在我国工业界的发展提供了有益的探索。     

Grain Refinement in a Low Carbon Steel Through Multidirectional Forging

 Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.     

20CrH温锻内星齿轮混晶原因分析及工艺改进

特钢厂生产的20CrH特殊钢棒材，下游用户温锻制作内星轮后，经965℃×6 h渗碳热处理后发现混晶现象。采用光学显微镜观察并设计热处理试验验证，结果表明：锻造变形温度不均及锻后保温温度偏低，导致在后续渗碳过程中局部奥氏体晶粒出现异常长大而产生混晶。将内星轮温锻后保温温度由710℃提高至900℃,能有效改善混晶现象，为同类特殊钢零部件温锻的工艺设计提供指导。     

Characterization of Steel Thixoforming Tool Materials by High Temperature Compression Tests

The experimental set‐up and the results of high temperature compression tests for the characterization of tool materials for steel thixoforming are presented. The scope of this test is to reproduce the load profile of steel thixoforming processes consisting of mechanical, thermal, tribological, and chemical components on the forming mould. Tool materials were chosen following a concept within the Collaborative Research Center ‐ SFB 289 ‐ “Forming of metals in the semi‐solid state and their properties”. Three materials groups are distinguished: thin film deposited by physical vapor deposition (PVD) and plasma assisted chemical vapour deposition (PACVD), thick coatings (thermal spraying), and bulk ceramic materials. Samples were characterized using scanning electron microscopy (SEM), electron‐dispersive spectroscopy (EDS) and X‐Ray diffraction analysis (XRD). The results show varying resistance of the tool materials concerning the load profile. In order to provide an appropriate tool solution for the thixoforming of steels, different load profiles within the forming moulds are identified and the corresponding tool part is made from that material with the best performance.     

HRB400热轧带肋钢筋强度不合格原因分析

针对HRB400热轧带肋钢筋强度不合格的问题，采用化学分析、金相检验、实物测量等方法进行了分析，结果表明合金元素偏析严重、晶粒粗大、尺寸超差、内部夹杂物缺陷是造成强度不合格的主要原因，提出了严格控制主要元素成分、提高钢水纯净度、降低终轧温度等改进措施和建议。     

广东省建筑用钢材质量的现状

通过对全省约60家钢厂的建筑用钢材的质量抽查，认为基本达到相关产品的国家标准或行业标准；但在钢材的包装、标志方面，很多钢厂不够重视．由于受市场因素影响，整个行业普遍生产“负公差”钢材．通过对抽查钢材进行化学成分和物理性能试验、分析、统计表明：热轧带肋钢筋合格率达94．4％，钢筋力学性能σs、σb略高出标准50～70MPa，冷弯合格率很好．冷轧带肋钢筋和冷轧扭钢筋的合格率分别为62．5％，78．6％，此类钢筋力学性能整体偏高，不合格的主要因素是冷弯开裂、延伸率低．热轧再生钢筋合格率为90．9％，我省这类钢筋的产量很少．热轧盘条和热轧光圆钢筋的合格率均为100％，显示我省生产这两种钢筋已达到较成熟的水平．     

Technology innovations on high quality special steel products

Because special steels are the basic materials for industrialization,a national R&D program on special steel technology for high quality products have been granted to promote the special steel production and applications since 2008.Since then,great progresses have been achieved on ferritic stainless steel sheets,heat resistance steel pipes and tubes,microalloyed forging steel bars,and mould steel forgings for hot working. The ratio of ferritic stainless steel sheets produced by TISCO and Baosteel has been promoted through technology innovations and increased 42%and 48 in 2009 respectively.439M steel sheets have been used to exhaust system,and 444 steel sheets have been applied to kitchen and architecture.The production technologies for heat resistance steel pipes and tubes(T/P92,S3043,S31042 steels) have been developed in Baosteel and Pansteel to meet the market requirements.Meanwhile,the round bloom technology has been initiated in Xingcheng Steel.The new technologies for microalloyed forging steels,low cost steel bar,and tailored steel and components,were proposed by CISRI based on the understanding of precise chemical composition and segregation control.And the applications of microalloyed forging steel bars have been promoted remarkably.The researchers have developed high quality mould steel technologies,heavy section forgings of 718 steel,high premium H13 steel blocks and large diameter mandrels used for seamless pipe rolling.The technology innovations of the program could lead to the progress of production technology in special steel sheets,pipes,bars and forgings,and meet the demands from market.For the moment,it is actually believed that there still strong requirements for the technology innovations on special steels.     

粉末热锻制备9Cr-ODS钢的微观组织和力学性能研究

摘要：ODS钢因其优异的高温力学性能和抗辐照能力被认为是新一代核反应堆最具潜力的结构材料之一。在机械合金化后,通过粉末热锻成型的方法制备了一种低活化9Cr-ODS钢。采用SEM、XRD、TEM及拉伸实验等研究了粉末形貌和粒度随球磨时间的变化规律,以及热处理后9Cr-ODS钢的微观组织及力学性能。实验结果表明,球磨至50 h后,粉末的粒度、晶粒尺寸和晶格畸变趋于稳态。热处理后的9Cr ODS钢成功获得了具有高密度位错的回火马氏体组织,晶粒细小,析出相为M23C6碳化物及Y-Ti-O型氧化物。氧化物颗粒的平均直径为10.2nm,数密度约为1.3×1022m-3。粉末热锻成型的9Cr-ODS钢的致密度达到了99.4%,并具有优良的强塑性,其室温抗拉强度和屈服强度分别为910MPa和750MPa,700℃时分别为200MPa和160MPa。     

基于图象处理的棒材自动计数技术

利用面阵CCD摄象机采集打捆后棒材的端面图象，通过合适的阈值将灰度图象转换成二值图象，以消除棒材图象区域中由于油污造成的孔洞和棒材区域间的粘连现象。根据距离变换思想，提出了图象距离概念，通过计算并比较棒材区域各象素点的图象距离，确定了各根棒材的中心，从而实现了从图象中自动计算棒材的数目。对现场采集到的图象进行试验，结果验证了这种方法的有效性。     

Wolfgang Bleck has taken over the chair of „steel research” Editorial Board from Oskar Pawelski

VDEh, the German Iron and Steel Institute, has appointed Professor Dr.-Ing. Wolfgang Bleck to the chair of steel research” Editorial Board in their 1998 annual meeting. Professor Dr.-Ing. Oskar Pawelski who had been the Board's very first chairman since 1985 finished his official carreer with the celebration of his 65～ birthday at the end of April 1998. Simultaneously had he retired from the chair of ?steel research” Editorial Board. When the editor's choice fell on Wolfgang Bleck as O. Pawelski's successor, this was not only to honour Professor Bleck's services to ?steel research”, but to ensure continuity of both the high level of this internationally esteerned scientific journal and the cooperation with all members of the Editorial Board. The new young chairman is expected to carry on the tradition of ?steel research” for another era. So let us take the opportunity to introduce Professor Dr.-Ing. Wolfgang Bleck to the ?steel research” readership.     

VN合金化对HRB400钢筋力学性能的影响

研究了添加VFe合金与VN合金生产HRB400钢筋对力学性能的影响及其强化机理。结果表明:采用VN合金生产的HRB400钢筋强度明显提高,VN的细化效果比VFe好,大量细小弥散的V(C,N)析出相是钒氮钢筋强度增加的主要原因。同时分析认为,为确保钢筋力学性能合格,炼钢工序应提高化学成分的均匀稳定性,其中钒含量应控制在0.05%以上,轧钢工序应严格执行加热和停轧降温制度。HRB400钢筋最佳的生产工艺是VN复合微合金化加控轧控冷工艺。